The Upper House of the Japanese Diet approved the bill by a vote of 221-12, less than a week after the measure cleared the lower house with almost no opposition. Violators risk up to two years in prison or fines up to two million yen (about $25,000).

Opponents of the bill worry it will lead to unnecessary prosecutions because of the way it is written. To face charges, a person must be aware that the material is illegal to download.

"We shouldn't risk making the general public — including youths — the subject of criminal investigations," said Upper House member Yuko Mori, as quoted in the Japan Times.

Japanese attorney Toshimitsu Dan told IT Media that even watching a YouTube video could be grounds for arrest "if the viewer is aware that downloading [such material] is illegal."

Unauthorized uploading and downloading of copyrighted material such as music, movies and video games have been illegal in Japan for years, but until now only uploaders were subject to criminal penalties: up to 10 years in prison or fines as much as 10 million yen ($125,000), according to the Times.